From aac5c57ee167230cea466064951daf06e42197b9 Mon Sep 17 00:00:00 2001 From: Jan Hubicka Date: Sun, 17 Nov 2024 01:21:04 +0100 Subject: [PATCH] Add __builtion_unreachable to vector::size(), vector::capacity() This patch makes it clear that vector sizes and capacities are not negative. With recent change to ipa-fnsummary this should not affect inlining and improves codegen of some vector manipulation functions. I tested clang build. Looking for throw_bad calls there are only 3 called considerably often (bad_allloc, bad_array_new_length and function_callv). The patch seems to reduce bad_alloc and bad_array_new_length calls considerably: bad_alloc 380->147 bad_array_new_length 832->128 libstdc++-v3/ChangeLog: PR tree-optimization/109442 * include/bits/stl_vector.h: (vector::size(), vector::capacity()): Add __builtin_unreachable call to announce that size and capacity are non-negative. gcc/testsuite/ChangeLog: PR tree-optimization/109442 * g++.dg/tree-ssa/pr109442.C: New test. --- gcc/testsuite/g++.dg/tree-ssa/pr109442.C | 2 +- libstdc++-v3/include/bits/stl_vector.h | 14 +++++++++++--- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr109442.C b/gcc/testsuite/g++.dg/tree-ssa/pr109442.C index ec40c470c8d..ea5800aa134 100644 --- a/gcc/testsuite/g++.dg/tree-ssa/pr109442.C +++ b/gcc/testsuite/g++.dg/tree-ssa/pr109442.C @@ -1,5 +1,5 @@ // { dg-do compile { target c++11 } } -// { dg-options "-O1 -fdump-tree-optimized" } +// { dg-options "-O2 -fdump-tree-optimized" } #include #define T int T vat1(std::vector v1) { diff --git a/libstdc++-v3/include/bits/stl_vector.h b/libstdc++-v3/include/bits/stl_vector.h index df48ba3377f..3ece16b2fac 100644 --- a/libstdc++-v3/include/bits/stl_vector.h +++ b/libstdc++-v3/include/bits/stl_vector.h @@ -1114,7 +1114,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR size_type size() const _GLIBCXX_NOEXCEPT - { return size_type(this->_M_impl._M_finish - this->_M_impl._M_start); } + { + ptrdiff_t __dif = this->_M_impl._M_finish - this->_M_impl._M_start; + if (__dif < 0) + __builtin_unreachable (); + return size_type(__dif); + } /** Returns the size() of the largest possible %vector. */ _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR @@ -1201,8 +1206,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER size_type capacity() const _GLIBCXX_NOEXCEPT { - return size_type(this->_M_impl._M_end_of_storage - - this->_M_impl._M_start); + ptrdiff_t __dif = this->_M_impl._M_end_of_storage + - this->_M_impl._M_start; + if (__dif < 0) + __builtin_unreachable (); + return size_type(__dif); } /**